Study looks at link between caffeine gene, heart attack

In coffee drinker study, mutation slows processing of stimulant.

In coffee drinker study, mutation slows processing of stimulant.

March 08, 2006|DENISE GELLENE Los Angeles Times

An extra cup of coffee increased the risk of a first heart attack in people with a defect in the gene responsible for breaking down caffeine, researchers reported Tuesday. But people with a normal caffeine-processing gene could drink as much coffee as they liked with no added heart attack risk, scientists said. Coffee is among the most widely consumed beverages in the world, and Americans spend more than $17 billion a year on lattes, cappuccinos and just plain joe. Slightly more than half of adults in the U.S. start their mornings with a cup of coffee. Coffee drinkers average three cups daily. The report in the Journal of the American Medical Association helped explain why earlier studies on the health effects of coffee produced conflicting results. None of the other studies looked at genetic differences among coffee drinkers. The study compared 2,000 people who had suffered a first heart attack to an equal number of healthy people. Participants in the study were asked about their coffee consumption and tested for a mutation in the caffeine-processing gene, the CYP1A2 gene. People with the genetic defect process caffeine up to four times more slowly than people with a normal gene, said Ahmed El-Sohemy, a University of Toronto researcher involved in the study. Caffeine causes blood vessels to constrict, which can trigger an increase in blood pressure. The longer caffeine remains in the bloodstream, the greater potential for harm, El-Sohemy said. There is no commercial test for the CYP1A2 gene, which scientists have known about since the 1990s. All people have two copies of the gene. People with mutations in one or both genes will break down caffeine slowly. El-Sohemy said the gene mutation is common and that about half of the residents in large urban centers have the mutated gene. El-Sohemy's study was conducted in Costa Rica, where a member of his team had been performing other research. Researchers found that a single cup of coffee daily did not increase the heart attack risk in people with the genetic defect. But those who drank two to three cups of coffee daily faced a 36 percent increased risk of a first heart attack. Those consuming four or more cups of coffee had a 64 percent higher risk. Women with the defective gene had a higher risk than men, and younger people with the defect faced worse odds than older coffee drinkers. El-Sohemy said a second study was needed to confirm his findings. The American Heart Association dietary guidelines said one to two cups of coffee daily do not appear harmful. "I would not change dietary guidelines based on one study," El-Sohemy said. Coffee had a protective effect for people with normal caffeine-processing genes, the study found. Drinking up to three cups of coffee daily reduced the risk of a first heart attack by 22 percent in people with normal CYP1A2 genes. El-Sohemy said coffee contains antioxidants and other beneficial chemicals.